1. Field of the Invention
The present general inventive concept relates to an inkjet image forming apparatus, and more particularly, to a scanning type inkjet image forming apparatus which performs a printing operation with high resolution.
2. Description of the Related Art
Scanning type inkjet image forming apparatuses eject ink from a printhead that is reciprocated in a direction that is perpendicular to a feeding direction of a print medium while being spaced apart from a top side of the print medium by a predetermined gap, thereby forming an image. Printing quality is a very important factor in inkjet image forming apparatuses. Thus, the scanning type inkjet image forming apparatuses perform a printing operation using a shingling process, so as to improve printing quality. Here, the shingling process is a technique in which printing is repeatedly and overlappingly performed while finely moving a printing position of the printhead.
In an effort to enhance the printing quality, U.S. Pat. No. 4,999,646 describes a conventional shingling process performed by an image forming apparatus. FIG. 1 illustrates dot patterns printed with the conventional shingling process. As illustrated in FIG. 1, a predetermined portion of dot patterns is overlappingly printed using one nozzle unit during a first scanning operation and second scanning operation to enhance uniformity and consistency of dots deposited on a print medium. In this case, a feeding speed and a printing speed of the print medium are substantially reduced. In addition, when portions of nozzles are damaged or certain nozzles are malfunctioning, and a printing operation is performed in a normal mode (i.e., without using the shingling process), a portion of the print medium that corresponds to the portions of the nozzles that are damaged or the malfunctioning nozzles is not printed. As a result, printing defects such as a white line (or the like) may occur.
In the above-described conventional image forming apparatus, a high-speed printing operation cannot be performed. Thus, a scanning type inkjet image forming apparatus having an improved structure to perform high-speed printing operation is needed.